This invention relates to a transistor deflection circuit for a television receiver.
Solid state television receivers have generally utilized either silicon controlled rectifiers (SCR's) or transistors to provide switching necessary to develop a varying current magnitude in a winding of a deflection yoke utilized in conjunction with a kinescope to provide electrode beam deflection. These television receivers have utilized both saddle and toroidal yoke designs. The toroidal yokes have many advantages over the saddle yokes, however, toroidal yokes are, generally, of a lower impedance than saddle yokes.
SCR deflection systems are ideally suited for use with toroidal yokes because of their power switching characteristics but are, generally, more complex than transistor deflection systems of the same deflection power-deliverying capability.
Currently there are no practical deflection transistors available which will switch the currents required to be supplied to toroidal yokes utilized with large deflection angle (e.g. 110.degree.) kinescopes during the trace portion of the deflection cycle while not breaking down under voltages developed during the retrace portion of the deflection cycle. However, by transforming the toroidal yoke impedance to a higher impedance, currently available transistors can be made to operate within limit specifications.
Deflection circuit designs utilizing transistors in conjunction with transformed yoke impedances have placed high capacitance and high current type capacitors required to establish the shape of the trace portion of the deflection cycle directly in series with the yoke. Also, the power supply providing B+ to this type deflection circuit generally requires high capacitance and high voltage type capacitors.
When an adjustment for centering of the raster on the face of the kinescope is required, a centering network comprising non-symmetrical components and a current integration inductor has been coupled in parallel with the yoke in order to create an adjustable magnitude and polarity direct current through the yoke during the trace portion of the deflection cycle. It would be desirable to reduce the complexity and cost of such a centering circuit.